Instant messaging privacy- will AIM/Plaxo list my email address publicly?

I am thinking of installing AIM Instant Messaging, but have a question about privacy.

The AIM web site has a brief note about its new and improved PLAXO service, which “helps you synchronize your address books”. The Plaxo function is built-in to the AIM Instant messaging, and automatically plugs into email programs such as Outlook.

According to wiki, Plaxo is a central server that keeps your email address, and when you change it, it notifies all other people who use Plaxo and have your address.

Am I paranoid–or is this a friendly form of Big Brother keeping track of me?
Specific questions:

  1. Suppose I open an instant messaging account at AIM with a username of “john”. Will Plaxo go into my personal emails in Outlook , identify my addresss as chappachula @, and then make that info available to all other Plaxo users? Or just the users on my AIM buddy list?

  2. Suppose that in the future, I decide to unlist a buddy who I’ve decided is a weirdo --will he still be able to find my real email address?

  3. And if I change my Outlook email address will the whole world be able to track the change through Plaxo?

  4. what about viruses? If AIM and Plaxo integrate themselves into the Outlook stored on my PC at home, will that make it easier for hackers to read the list of all my email contacts, and send spoofed messages to them that look like they came from me?